This is the current per capita GDP expressed relative to the United State (US=100) in each year. More information is available at http://pwt.econ.upenn.edu/Documentation/append61.pdf
For proper citation, see http://pwt.econ.upenn.edu/php_site/pwt_index.php
Source Indicator: y2
Source: University of Pennsylvania
Release: Penn World Table 7.1
University of Pennsylvania, Purchasing Power Parity Converted GDP Per Capita Relative to the United States, average GEKS-CPDW, at current prices for Estonia [PGD2USEEA621NUPN], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/PGD2USEEA621NUPN/, July 28, 2015.